Polyolefin fibers containing antimicrobial siloxane quaternary ammonium salts

ABSTRACT

Fibers having antimicrobial properties made from a melt-extrudable thermoplastic composition. The thermoplastic composition includes a thermoplastic polyolefin and an additive. The additive is an antimicrobial siloxane quaternary ammonium salt which can be either of two general classes: (1) a trisiloxane having a pendent quaternary ammonium group and a molecular weight of from about 600 to about 1,700; and (2) an ABA-type siloxane having a polydispersity of up to about 3.0 and a weight-average molecular weight of from about 800 to about 2,000, in which a central siloxane moiety is terminated at each end by a quaternary ammonium salt group. The anion in general can be any anion which does not adversely affect the thermal stability of the salt.

This application is a division of application Ser. No. 08/686,228, nowU.S. Pat. No. 5,770,010 entitled "ANTIMICROBIAL SILOXANE QUATERNARYAMMONIUM SALTS" and filed in the U.S. Patent and Trademark Office onJul. 23, 1996, which is a division of application Ser. No. 08/450,451,filed on May 25, 1995, now U.S. Pat. No. 5,569,732, which is a divisionof application Ser. No. 08/249,788, filed on May 26, 1994, now U.S. Pat.No. 5,567,372, which is a continuation-in-part of application Ser. No.08/076,529, filed on Jun. 11, 1993, now abandoned. The entireties ofthese applications are hereby incorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATION

Polysiloxane quaternary ammonium salts are employed in a method ofpreparing a nonwoven web having delayed wettability, which method isdescribed and claimed in copending and commonly assigned applicationSer. No. 08/076,528, filed on Jun. 11, 1993 in the names of RonaldSinclair Nohr and John Gavin MacDonald.

BACKGROUND OF THE INVENTION

The present invention relates to siloxane quaternary ammonium salts.

Traditional melt-extrusion processes for the formation of a nonwoven webfrom a thermoplastic polymer typically involve melting the thermoplasticpolymer, extruding the molten polymer through multiple orifices to forma plurality of threadlines or filaments, attenuating the filaments byentrainment in a rapidly moving first stream of gas, cooling thefilaments with a second stream of gas, and randomly depositing theattenuated filaments, or fibers, on a moving foraminous surface. Themost common and well known of these processes are meltblowing,coforming, and spunbonding. The nonwoven webs obtained by theseprocesses are widely used in a variety of products, but especially insuch disposable absorbent products as diapers; incontinent products;feminine care products, such as tampons and sanitary napkins; wipes;sterilization wraps; surgical drapes and related materials; hospitalgowns and shoe covers; and the like, to name but a few.

There is an increasing interest in the utilization of nonwoven webswhich have antimicrobial properties. The traditional means for providingsuch webs has been to simply topically treat the already-formed nonwovenweb with a solution of an antimicrobial agent. This involves additionalprocessing steps and typically requires drying the treated web to removewater or other solvent in which the antimicrobial agent is dissolved.Because the antimicrobial agent typically is water soluble, it is easilyremoved from the web by water. This obviously is a serious disadvantagefor nonwoven webs which will be repeatedly used or placed in contactwith water.

It is, of course, known to melt-extrude a mixture of an additive and athermoplastic polymer to prepare fibers. In some instances, the additivemust be forced, or "bloomed", to the surfaces of the fibers bysubjecting them to a post-heat treatment step. The additive to bebloomed usually is a nonionic surfactant, such as an alkylphenoxypolyether.

In other instances, a surface-segregatable, melt-extrudablethermoplastic composition is employed which includes at least onethermoplastic polymer and at least one additive which typically is apolysiloxane polyether. Such surface segregation now appears to be bestexplained on the basis of micelle formation. Briefly, a relatively lowmolecular weight additive is miscible with the polymer at melt extrusiontemperatures, forming an unstable emulsion characterized by metastablemicellar structures. Upon extrusion, during which a rapid increase inshear rate is experienced, the additive is believed to break free fromthe metastable micelle "aggregate" and molecularly diffuse to the fibersurfaces. Such diffusion is driven in part by both a loss of additivecompatibility and a potential drop in interfacial free energy.

However, the goal of providing a compound to be included as an additivein a thermoplastic composition for the preparation of antimicrobialnonwoven webs presents at least three challenges. First, the additiveshould undergo surface segregation upon melt-extruding theadditive-containing thermoplastic composition to form fibers. As alreadynoted, the compounds of the present invention do, in fact, migrate tothe fiber surfaces. The alternative is to use an amount of the additivewhich is sufficiently large so as to assure that at least some additiveis present at the surfaces of the fibers, but this significantlyincreases fiber spinning problems and increases the possibility ofadditive degradation. In addition, both material and manufacturing costsare increased. Second, assuming the additive is present at the surfacesof the fibers, it must be capable of imparting antimicrobial propertiesthereto. Third, the additive must be relatively stable during themelt-extrusion process.

SUMMARY OF THE INVENTION

In response to the discussed difficulties and problems encountered inthe prior art, two classes of novel siloxane quaternary ammonium saltsnow have been discovered which meet all three of the above requirementsand, as will be demonstrated later, do so to an unexpected degree. Thatis, such salts undergo surface segregation upon melt-extrusion of thethermoplastic composition of which they are a part, they impartantimicrobial properties to the surfaces of the fibers, and they arerelatively stable during the melt-extrusion process. In addition, theyform an extended antimicrobial surface, i.e., an antimicrobial surfacewhich extends below the air/fiber interfacial surface, which affords thepotential for durable antimicrobial properties.

In light of the unexpected results described herein, it appears that thecompounds of the present invention enhance the loss of additivecompatibility just described. This increases the rate of diffusion whichforces more additive molecules to the surface before fibersolidification stops the migration. Consequently, unexpectedly highlevels of additive were observed to have migrated to the surfaces of thefibers.

Accordingly, the present invention provides a siloxane quaternaryammonium salt having either the general formula A, ##STR1## wherein:

(1) each of R₁ -R₇ is independently selected from the group consistingof monovalent C₁ -C₂₀ alkyl, phenyl, and phenyl-substituted C₁ -C₂₀alkyl groups, in which each phenyl can be substituted or unsubstituted;

(2) each of R₈ and R₉ is a monovalent group independently selected fromthe group consisting of (a) hydrogen and (b) monovalent alkyl,cycloalkyl, aryl, and heterocyclic groups and combinations thereofhaving up to about 30 carbon atoms, except that both R₈ and R₉ cannot behydrogen; or, when taken together in combination with the carbon atom towhich they are attached, R₈ and R₉ represent a carbonyl group;

(3) each of R₁₀ and R₁₁ is an independently selected monovalent C₁ -C₂₀alkyl group;

(4) a represents an integer from 1 to about 20;

(5) b represents an integer from 1 to about 20;

(6) Z is a monovalent group having from about 8 to about 30 carbon atomsand selected from the group consisting of alky, cycloalkyl, aryl, andheterocyclic groups, and combinations thereof, wherein Z is terminatedby an alkyl moiety which includes at least about 8 carbon atoms in asingle continuous chain;

(7) Y₁ is an anion; and

(8) the siloxane quaternary ammonium salt has a molecular weight of fromabout 600 to about 1,700;

or the general formula B, ##STR2## wherein:

(1) each of R₂₀ -R₂₃ is independently selected from the group consistingof monovalent C₁ -C₂₀ alkyl, phenyl, and phenyl-substituted C₁ -C₂₀alkyl groups, in which each phenyl can be substituted or unsubstituted;

(2) n represents an integer of from 1 to about 19;

(3) each of Q, and Q₂ represents an independently selected quaternaryammonium group having the general formula, ##STR3##

in which:

(a) R₂₄ is a monovalent alkyl group having from about 8 to about 30carbon atoms, at least about 8 carbon atoms of which make up a singlecontinuous chain;

(b) R₂₅ and R₂₆ are independently selected monovalent C₁ -C₂₀ alkylgroups;

(c) each of R₂₇ and R₂₈ is a monovalent group independently selectedfrom the group consisting of (i) hydrogen and (ii) monovalent alkyl,cycloalkyl, aryl, and heterocyclic groups and combinations thereofhaving up to about 30 carbon atoms, except that both R₂₇ and R₂₈ cannotbe hydrogen; or, when taken together in combination with the carbon atomto which they are attached, R₂₇ and R₂₈ represent a carbonyl group;

(d) c represents an integer of from 2 to about 20; and

(e) d represents an integer of from 2 to about 20;

(4) Y₂ represents an anion; and

(5) the siloxane quaternary ammonium salt has a polydispersity of up toabout 3.0 and a weight-average molecular weight of from about 800 toabout 2,000.

The present invention also contemplates a melt-extrudable compositionwhich includes at least one melt-extrudable material adapted to beshaped into a product by melt extrusion and at least one additive whichincludes a siloxane-containing moiety and an antimicrobial moiety.Melt-extruded products contemplated by the present invention include afiber and a nonwoven web which includes a plurality of fibers.

The additive is adapted to surface segregate upon extrusion of thecomposition to impart antimicrobial properties to a surface of theproduct. The antimicrobial moiety may be a quaternary ammonium saltmoiety. In general, the additive will be present in the composition at alevel which is sufficient to impart antimicrobial properties to theproduct. The composition may be a melt-extrudable thermoplasticcomposition. In one embodiment, the melt-extrudable thermoplasticcomposition is a polyolefin. For example, the composition may include atleast one thermoplastic polyolefin and at least one additive havingeither the general formula A or the general formula B, above.

The present invention further contemplates that the quaternary ammoniumsalt moiety of the additive may be part of a siloxane quaternaryammonium salt. Desirably, the siloxane quaternary ammonium salt willhave either general formula A or general formula B. The thermalstability of a salt represented by general formula A or B is enhanced bythe presence of no more than one hydrogen atom on each β-carbon atom ofthe quaternary ammonium salt moiety thereof. Desirably, each β-carbonatom will not have any hydrogen atoms attached to it.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-10 illustrate the various chemical reactions involved inpreparing compounds of the present invention as described in Examples1-10.

FIGS. 11-15 are bar graphs of ESCA values for silicon and nitrogen,expressed as percentages of the theoretical values, of antimicrobialnonwoven webs prepared in accordance with the present invention.

FIGS. 16 and 17 are three-dimensional bar graphs of log drop data fortwo microorganisms exposed to antimicrobial nonwoven webs prepared inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term "stable" is used with reference to anantimicrobial compound of the present invention to mean that thecompound is sufficiently thermally stable during melt processing to formfibers in which the compound has segregated to the surfaces of thefibers in an amount which is sufficient to impart antimicrobial activitythereto. Thus, some thermal degradation is acceptable, provided at leastabout 65 percent of the compound present in the thermoplasticcomposition to be melt extruded survives the melt extrusion process.

For convenience, the phrase "internal additive," as well as variationsthereof, is used herein with reference to the compounds of the presentinvention. The phrase implies, as taught herein, the inclusion of acompound of the present invention in a melt-extrudable material, e.g., athermoplastic polymer, to give a melt-extrudable or thermoplasticcomposition which subsequently is melt-processed to form a nonwoven webor other shaped article.

As used herein, the terms "shaped article" and "product" are synonymsand are meant to include any article or product which is formed by amelt-extrusion process, regardless of the size or shape of the article.As a practical matter, the present disclosure is directed primarily tomelt-extruded fibers and nonwoven webs comprised of such fibers.Nevertheless, other shaped articles or products are deemed to comewithin the spirit and scope of the present invention.

The term "extended antimicrobial surface" is used herein to refer to theregion of a fiber (or other shaped article) prepared in accordance withthe present invention which extends from the interfacial surface, e.g.,the air/fiber (or nonfiber/fiber) interface, to a depth of roughly 100 Å(or perhaps even further), which region consists essentially ofantimicrobial compound.

The term "melt-extrudable material" is meant to include any materialadapted to be shaped into a product by melt extrusion. Thus, the termincludes both thermosetting and thermoplastic materials. Particularlyuseful thermoplastic materials are the thermoplastic polyolefins.

In general, the term "thermoplastic polyolefin" is used herein to meanany thermoplastic polyolefin which can be used for the preparation ofshaped articles by melt extrusion, e.g., fibers and nonwoven webs.Examples of thermoplastic polyolefins include polyethylene,polypropylene, poly(1-butene), poly(2-butene), poly(1-pentene),poly(2-pentene), poly(3-methyl-1-pentene), poly(4-methyl-1-pentene),1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene,polychloroprene, polyacrylonitrile, poly(vinyl acetate),poly-(vinylidene chloride), polystyrene, and the like. In addition, suchterm is meant to include blends of two or more polyolefins and randomand block copolymers prepared from two or more different unsaturatedmonomers.

Particularly useful polyolefins are those which contain only hydrogenand carbon atoms and which are prepared by the addition polymerizationof one or more unsaturated monomers. Examples of such polyolefinsinclude, among others, polyethylene, polypropylene, poly(1-butene),poly(2-butene), poly(1-pentene), poly(2-pentene),poly(3-methyl-1-pentene), poly(4-methyl-1-pentene),1,2-poly-1,3-butadiene, 1,4-poly-1,3-butadiene, polyisoprene,poly-styrene, and the like. Because of their commercial importance, themost significant polyolefins are polyethylene and polypropylene.

The term "monovalent C₁ -C₂₀ alkyl" is used herein to encompass suchmonovalent groups as methyl, ethyl, propyl, isopropyl, butyl, 2-butyl,isobutyl, 1-butyl, pentyl, isopentyl, 2-pentyl, 3-pentyl,2-methyl-2-butyl, hexyl, 2-hexyl, 3-hexyl, 4-methyl-2-pentyl,3,3-dimethylbutyl, heptyl, 2-heptyl, 3-heptyl, 4-heptyl,3-methyl-2-hexyl, 2,3-dimethylpentyl, octyl, 2-octyl, 3-octyl, 4-octyl,3-ethylhexyl, 3-methylheptyl, nonyl, 3-nonyl, 5-nonyl, 4-methyloctyl,isodecyl, 2,5,5-trimethylheptyl, undecyl, dodecyl, 3-tridecyl,tetradecyl, 2-tetradecyl, 3,4,6-trimethylundecyl, 4-pentadecyl,hexadecyl, isoheptadecyl, octadecyl, 2-octadecyl, nonadecyl, eicosyl,and the like. The phrase "monovalent phenyl and phenyl-substituted C₁-C₂₀ alkyl groups, in which each phenyl can be substituted orunsubstituted" includes by way of illustration only, phenyl, o-tolyl,m-tolyl, p-tolyl, 3,4-dimethylphenyl, 3,5-dimethylphenyl,3-methyl-4-ethylphenyl, benzyl, 2,4-diethylbenzyl, 2-phenylpropyl,2-(3-methoxyphenyl)-butyl, phenylpentyl, 3-(4-methoxyphenyl)hexyl,4-phenyloctyl, 3-benzylundecyl, 5-phenyl-2-dodecyl,3-(Q-tolyl)tetradecyl, 3-phenoxyheptadecyl,2,4-dimethyl-6-phenylhexadecyl, phenyleicosyl, and the like.

As used herein, the phrase "having up to about 30 carbon atoms", whenused in conjunction with the phrase "monovalent alkyl, cycloalkyl, aryl,and heterocyclic groups and combinations thereof", means that each typeof group and combinations thereof can contain up to about 30 carbonatoms. Thus, the approximately 30 carbon atoms is a limit on the totalnumber of carbon atoms in the group, regardless of the natures ornumbers of groups of which the "monovalent group" is composed. The lowerlimit is the minimum number of carbon atoms permitted by the type ofgroup, as is well known by those having ordinary skill in the art. Byway of illustration, a cycloalkyl group must have at least three carbonatoms in the ring. As a practical matter, however, cycloalkyl groupshaving from 3 to 5 carbon atoms are more strained than rings having 6 ormore carbon atoms and, as a consequence, may be less stable. The use oflarger ring structures, i.e., cycloalkyl groups having at least 6 carbonatoms, will reduce such strain-related instability.

Examples of the various monovalent alkyl, cycloalkyl, aryl, andheterocyclic groups and combinations thereof include, by way ofillustration only, the monovalent C₁ -C₂₀ alkyl groups exemplified aboveand such groups as heneicosyl, 6-(1-methylpropyl)-2-heptadecyl,3-docosyl, 5-ethylheneicosyl, hexacosyl, 3-methylpentacosyl, heptacosyl,3,7,8-trimethyltetracosyl, octacosyl, 5-octacosyl, 2-nonacosyl,4-propylhexacosyl, 3-triacontyl, 6-ethyl-2-octacosyl, cyclopropyl,methylcyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,3-methylcyclohexyl, 2-ethylcyclopentyl, 2-bicyclo 2.2.1!heptyl,cyclooctyl, 4-ethylcyclohexyl, 8-bicyclo 3.2.1!octyl, cyclononyl,cyclodecyl, 2,3,5-trimethylcycloheptyl, 2-bicyclo 4.4.0!decyl,cyclopentadecyl, cycloheneicosyl, cyclohexacosyl, cyclotriacontyl,phenyl, o-tolyl, m-tolyl, p-tolyl, 3,4-dimethylphenyl,3,5-dimethylphenyl, 3-methyl-4-ethylphenyl, benzyl, 2,4-diethylbenzyl,4-hexadecylbenzyl, 3-methyl-5-phenylhexyl, 4-cyclohexylphenyl,1-naphthyl, 2-naphthyl, 1-anthracyl, 9,10-dihydro-2-anthracyl,1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl,9-phenanthryl, 2-pentacenyl, 1-comenyl, phenyl, 1-naphthyl, 2-naphthyl,o-tolyl, m-tolyl, P-tolyl, 3,4-dimethylphenyl, 3,5-dimethylphenyl,3-methyl-4-ethylphenyl, pyrrolidinyl, piperidino, 2-piperidinoethyl,3-piperidyl, 2-(trimethylsilyl)ethyl, 1-biphenylyl, benzyl,2,4-diethylbenzyl, 4-hexadecylbenzyl, 3-methyl-5-phenylhexyl,4-cyclohexylphenyl, 2-(trimethylsilyl)ethyl, 1-biphenylyl,cyclohexylmethyl, 4-cyclopentylhexyl, and the like.

Based on the foregoing, examples of various subgroups, such asmonovalent C₆ -C₂₈ alkyl groups, monovalent C₈ -C₂₃ alkyl groups, andthe like will be readily determined by those having ordinary skill inthe art. In addition, groups such as those listed above may not besuitable in every instance. Stated differently, a particular grouplisted above may not meet all of the requirements for a givensubstituent. In such case, it is only necessary to add to the particulargroup whatever is necessary for it to meet the requirements for thegiven substituent. For example, as is explained in detail hereinafter,some groups should have a terminal alkyl moiety which includes at leastabout 8 carbon atoms in a single continuous chain. A benzyl group doesnot have the required terminal alkyl moiety. However, such requirementis met by, e.g., a 4-octylbenzyl group or a 4-hexadecylbenzyl group.Nevertheless, one having ordinary skill in the art can readilydetermine, based on the present disclosure, which groups are suitablefor any given substituent of an antimicrobial siloxane quaternaryammonium salt of the present invention without the need for undueexperimentation.

The siloxane quaternary ammonium salt of the present invention haseither the general formula A, ##STR4## wherein:

(1) each of R₁ -R₇ is independently selected from the group consistingof monovalent C₁ -C₂₀ alkyl, phenyl, and phenyl-substituted C₁ -C₂₀alkyl groups, in which each phenyl can be substituted or unsubstituted;

(2) each of R₈ and R₉ is a monovalent group independently selected fromthe group consisting of (a) hydrogen and (b) monovalent alkyl,cycloalkyl, aryl, and heterocyclic groups and combinations thereofhaving up to about 30 carbon atoms, except that both R₈ and R₉ cannot behydrogen; or, when taken together in combination with the carbon atom towhich they are attached, R₈ and R₉ represent a carbonyl group;

(3) each of R₁₀ and R₁₁ is an independently selected monovalent C₁ -C₂₀alkyl group;

(4) a represents an integer from 1 to about 20;

(5) b represents an integer from 1 to about 20;

(6) Z is a monovalent group having from about 8 to about 30 carbon atomsand selected from the group consisting of alkyl, cycloalkyl, aryl, andheterocyclic groups, and combinations thereof, wherein Z is terminatedby an alkyl moiety which includes at least about 8 carbon atoms in asingle continuous chain;

(7) Y₁ is an anion; and

(8) said siloxane quaternary ammonium salt has a molecular weight offrom about 600 to about 1,700;

or the general formula B, ##STR5## wherein:

(1) each of R₂₀ -R₂₃ is independently selected from the group consistingof monovalent C₁ -C₂₀ alkyl, phenyl, and phenyl-substituted C₁ -C₂₀alkyl groups, in which each phenyl can be substituted or unsubstituted;

(2) n represents an integer of from 1 to about 19;

(3) each of Q₁ and Q₂ represents an independently selected quaternaryammonium group having the general formula, ##STR6## in which: (a) R₂₄ isa monovalent alkyl group having from about 8 to about 30 carbon atoms,at least about 8 carbon atoms of which make up a single continuouschain;

(b) R₂₅ and R₂₆ are independently selected monovalent C₁ -C₂₀ alkylgroups;

(c) each of R₂₇ and R₂₈ is a monovalent group independently selectedfrom the group consisting of (i) hydrogen and (ii) monovalent alkyl,cycloalkyl, aryl, and heterocyclic groups and combinations thereofhaving up to about 30 carbon atoms, except that both R₂₇ and R₂₈ cannotbe hydrogen; or, when taken together in combination with the carbon atomto which they are attached, R₂₇ and R₂₈ represent a carbonyl group;

(d) c represents an integer of from 2 to about 20; and

(e) d represents an integer of from 2 to about 20;

(4) Y₂ represents an anion; and

(5) said siloxane quaternary ammonium salt has a polydispersity of up toabout 3.0 and a weight-average molecular weight of from about 800 toabout 2,000.

As stated above, each of R₁ -R₇ is independently selected from the groupconsisting of monovalent C₁ -C₂₀ alkyl, phenyl, and phenyl-substitutedC₁ -C₂₀ alkyl groups, in which each phenyl can be substituted orunsubstituted. In addition, each of R₁ -R₇, R₁₀, and R₁₁ canindependently selected monovalent C₁ -C₂₀ alkyl group. For example, eachof R₁ -R₇, R₁₀, and R₁₁ can be independently selected from the groupconsisting of monovalent C₁ C₄ alkyl, phenyl, and phenyl-substituted C₁-C₄ alkyl groups, in which each phenyl can be substituted orunsubstituted. As a further example, each of R₁ -R₇, R₁₀, and R₁₁independently can be a methyl group or an ethyl group. Desirably, eachof R₁ -R₇, R₁₀, and R₁₁ will be a methyl group.

As already noted, each of R₈ and R₉ independently is selected from thegroup consisting of (a) hydrogen and (b) monovalent alkyl, cycloalkyl,aryl, and heterocyclic groups and combinations thereof having up toabout 30 carbon atoms, except that both R₈ and R₉ cannot be hydrogen.Alternatively, when taken together in combination with the carbon atomto which they are attached, R₈ and R₉ represent a carbonyl group.

By way of example, each of R₈ and R₉ is an independently selectedmonovalent C₁ -C₄ alkyl group or, when taken together in combinationwith the carbon atom to which they are attached, R₈ and R₉ represent acarbonyl group. As a further example, each of R₈ and R₉ independentlycan be a methyl group or an ethyl group, or, when taken together incombination with the carbon atom to which they are attached, R₈ and R₉represent a carbonyl group. Desirably, each of R₈ and R₉ will be amethyl group or, when taken together in combination with the carbon atomto which they are attached, R₈ and R₉ represent a carbonyl group.

In general, each of a and b independently represent an integer from 1 toabout 20. For example, each of a and b independently represent aninteger from 1 to about 5. Desirably, a is 2 or 3 and b is 1 or 2.

Z is a monovalent group having from about 8 to about 30 carbon atoms. Itis selected from the group consisting of alkyl, cycloalkyl, aryl, andheterocyclic groups, and combinations thereof. In addition, Z isterminated by an alkyl moiety which includes at least about 8 carbonatoms in a single continuous chain. For example, Z can be an alkyl oralkylphenylalkyl group.

The phrase, "terminated by an alkyl moiety which includes at least about8 carbon atoms in a single continuous chain," means that, regardless ofthe nature of Z, it will be terminated by an alkyl moiety which includesat least about 8 carbon atoms in a single continuous chain. Thus, thisterminal alkyl moiety will be at the end of Z which is not covalentlybonded to the quaternary ammonium nitrogen atom. The carbon atoms makingup the single continuous chain can be substituted or unsubstituted,i.e., they can be any one or more of more of such groups as --CH₂ --,--CHR--, and --CRR'--, with the last group being, for example, one ofsuch groups as --CH₃, --CH₂ R, --CHRR', and --CRR'R", in which each ofR, R', and R" represent a substituent other than hydrogen. The term"single continuous chain" means only that the components of the chainare covalently bonded in series, as in the octyl group,

    --CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.3

in contrast with, for example, the 2-ethylhexyl or 2,3,4-trimethylpentylgroups, ##STR7## each of which also consists of 8 carbon atoms; thecarbon atoms in these latter two groups, however, are not present as asingle continuous chain. In certain embodiments, the terminal allylmoiety will not be branched. In other embodiments, the terminal alkylmoiety will have more than 8 carbon atoms in a single continuous chain.

In some embodiments, Z is a monovalent group having the general formula,##STR8## in which each of R₁₂ -R₁₄ is an independently selectedmonovalent alkyl group wherein the total number of carbon atoms in allof R₁₂ -R₁₄ is from about 6 to about 28 and at least one of R₁₂ -R₁₄contains at least about 6 carbon atoms in a single continuous chain.

In other embodiments, Z is a monovalent group having the generalformula, ##STR9## in which each of R₁₅ -R₁₉ is a monovalent groupindependently selected from the group consisting of hydrogen and alkyl,and wherein the total number of carbon atoms in all of R₁₅ -R₁₉ is fromabout 8 to about 23, with at least one of R₁₅ -R₁₉ having at least about6 carbon atoms in a single continuous chain. In some embodiments, eachof R₁₅, R₁₆, R₁₈, and R₁₉ is hydrogen and R₁₇ is hexadecyl.

In general, any anion can be employed in the siloxane quaternaryammonium salt of the present invention which does not contributesignificantly to the thermal instability of the salt. By way ofillustration only, examples of suitable anions include, among others,halo, such as iodo, bromo, chloro, and fluoro; sulfate; nitrate;phosphate; borate; acetate; p-toluenesulfonate (tosylate);trifluoromethanesulfonate (triflate); nonafluorobutanesulfonate(nonaflate); 2,2,2-trifiuoroethanesulfonate (tresylate);fluorosulfonate; and the like. In certain embodiments, the anion is ananion which is a weak base, such as p-toluenesulfonate (tosylate);trifluoromethanesulfonate (triflate); nonafluorobutanesulfonate(nonaflate); 2,2,2-trifluoroethanesulfonate (tresylate);fluorosulfonate; and the like. As used herein, the term "weak base"means a base having an ionization constant of less than one.

The siloxane quaternary ammonium salt having the general formula Atypically will have a molecular weight of from about 600 to about 1,700.In some embodiments, the salt will have a molecular weight of from about800 to about 1,400.

Turning now to the siloxane quaternary ammonium salt having the generalformula B, each of R₂₀ -R₂₃ is independently selected from the groupconsisting of monovalent C₁ -C₂₀ alkyl, phenyl, and phenyl-substitutedC₁ -C₂₀ alkyl groups, in which each phenyl can be substituted orunsubstituted. For example, each of R₂₀ -R₂₃ is independently selectedfrom the group consisting of monovalent C₁ -C₄ alkyl, phenyl, andphenyl-substituted C₁ -C₄ alkyl groups, in which each phenyl can besubstituted or unsubstituted. As a further example, each of R₂₀ -R₂₃independently can be a methyl group or an ethyl group. Desirably, eachof R₂₀ -R₂₃ will be a methyl group. As yet another example, n representsan integer of from about 5 to about 12.

With respect to Q₁ and Q₂, R₂₄ is a monovalent C₆ -C₃₀ alkyl group, atleast about 8 carbon atoms of which make up a single continuous chain,and R₂₅ and R26 are independently selected monovalent C₁ -C₂₀ alkylgroups. By way of example, R₂₅ and R₂₆ are independently selected C₁ -C₄alkyl groups. As another example, each of R₂₅ and R₂₆ independently is amethyl group or an ethyl group. As yet another example, each of R₂₅ andR₂₆ is a methyl group.

Each of R₂₇ and R₂₈ is independently selected from the group consistingof (i) hydrogen and (ii) monovalent alkyl, cycloalkyl, aryl, andheterocyclic groups and combinations thereof having up to about 30carbon atoms. Alternatively, when taken together in combination with thecarbon atom to which they are attached, R₂₇ and R₂₈ represent a carbonylgroup.

Generally, each of c and d independently represent an integer of from 2to about 20. Desirably, c is 3 or 4 and d is 2 or 3. The anion, Y₂, isas defined for the anion, Y₁, of the siloxane quarternary ammonium salthaving general formula A.

Finally, the siloxane quaternary ammonium salt having the generalformula B typically will have a polydispersity of up to about 3.0 and aweight-average molecular weight of from about 800 to about 2,000. Insome embodiments, the salt will have a weight-average molecular weightof from about 900 to about 1,400.

In general, the siloxane quaternary ammonium salts of the presentinvention are prepared by methods which are well known to those havingordinary skill in the art. For example, salts having the general formulaA are prepared from a glycidyloxypropyltrisiloxane as described inExamples 11-10, inclusive.

The melt-extrudable composition of the present invention includes atleast one melt-extrudable material adapted to be shaped into a productby melt extrusion and at least one additive which includes asiloxane-containing moiety and an antimicrobial moiety. The additive isadapted to surface segregate upon extrusion of the composition to impartantimicrobial properties to a surface of the product. Thesiloxane-containing moiety of the additive is largely responsible forthe ability of the additive to surface segregate. The additive alsoincludes an antimicrobial moiety, from which the additive derives itsantimicrobial properties.

As noted earlier, in some embodiments the composition is amelt-extrudable thermoplastic composition. In certain embodiments of amelt-extrudable thermoplastic composition, the melt-extrudable materialis a polyolefin. In still other embodiments, the antimicrobial moiety isa quaternary ammonium salt moiety. In still further embodiments, theadditive is present in the composition at a level which is sufficient toimpart antimicrobial properties to the product.

The present invention contemplates a composition which includes at leastone thermoplastic polyolefin and at least one additive having either thegeneral formula A or the general formula B, above. The additive can bemonomeric or polymeric. The additive also can be either a liquid or asolid at ambient temperature, although a liquid is easier to work with.In general, the additive will have a molecular weight, or weight-averagemolecular weight if polymeric, of from about 600 to about 3,000. In someembodiments, the additive will have a molecular weight or weight-averagemolecular weight of from about 600 to about 2,000. In other embodiments,the additive will have either the general formula A or the generalformula B, as defined hereinbefore.

Generally, the additive will be present in the thermoplastic compositionat a level which is sufficient to impart antimicrobial properties to thesurface of a shaped article formed by melt-extrusion of the composition.The additive typically will be present in the composition at a level offrom about 0.1 to about 3 percent by weight, based on the weight ofthermoplastic polyolefin. For example, the additive can be present inthe composition at a level of from about 0.1 to about 1.5 percent byweight.

The thermoplastic composition of the present invention can be preparedby any number of methods known to those having ordinary skill in theart. For example, the polymer in chip or pellet form and the additivecan be mixed mechanically to coat the polymer particles with additive.The additive can be dissolved in a suitable solvent to aid the coatingprocess, although the use of a solvent is not desired. The coatedpolymer then can be added to the feed hopper of the extruder from whichthe fibers or other shaped article will emerge. Alternatively, thecoated polymer can be charged to a heated compounder, such as a heatedtwin-screw compounder, in order to disperse the additive throughout thebulk of the polymer. The resulting thermoplastic composition typicallyis extruded as rods which are fed to a chipper. The resulting chips thenserve as the feed stock for a melt-processing extruder. In anothermethod, the additive can be metered into the throat of the hopper whichcontains the polymer in particulate form and which feeds the extruder.In yet another method, the additive can be metered directly into thebarrel of the extruder where it is blended with the molten polymer asthe resulting mixture moves toward the die.

Fibers having antimicrobial properties are readily prepared bymelt-extruding a melt-extrudable thermoplastic composition of thepresent invention through multiple orifices to form streams of moltencomposition which are cooled to form fibers. The melt-extrudablethermoplastic composition includes at least one thermoplastic materialand at least one additive which includes a siloxane-containing moietyand an antimicrobial moiety, which additive is adapted to surfacesegregate upon extrusion of the molten composition to impartantimicrobial properties to the surfaces of the fibers. For example, themolten composition is extruded at a shear rate of from about 50 to about30,000 sec⁻¹ and a throughput of no more than about 5.4 kg/cm/hour.

The method of the present invention for preparing a nonwoven web havingantimicrobial properties involves melting a melt-extrudablethermoplastic composition, extruding the molten composition throughmultiple orifices to form streams of molten composition which are cooledto form fibers which then are randomly deposited on a moving foraminoussurface to form a web, wherein the melt-extrudable thermoplasticcomposition includes at least one thermoplastic material and at leastone additive which includes a siloxane-containing moiety and anantimicrobial moiety, which additive is adapted to surface segregateupon extrusion of the molten composition to impart antimicrobialproperties to the surfaces of the fibers. For example, the moltencomposition is extruded at a shear rate of from about 50 to about 30,000sec⁻¹ and a throughput of no more than about 5.4 kg/cm/hour.

The present invention also provides several types of intermediates whichare useful for the preparation of the siloxane quaternary ammonium saltsdescribed and claimed herein. Procedures for preparing suchintermediates are well known to those having ordinary skill in the art,some of which are illustrated by certain of the examples. Suchintermediates are represented by general formulas C and D which follow:##STR10## wherein R₁ -R₇, R₁₀, R₁₁, a and b are as already defined, Z isa monovalent phenylalkyl group, such as benzyl and the like, and Y₉ isan anion as already defined. This type of compound can have a molecularweight of from about 470 to about 1,550. ##STR11## wherein R₁ -R₁₁, a,b, and Z₁ are as already defined and Y₁₀ is an anion as already defined.The compound can have a molecular weight of from about 450 to about1,500.

The present invention is further described by the examples which follow.Such examples, however, are not to be construed as limiting in any wayeither the spirit or scope of the present invention. Elemental analyseswere preformed by Schwarzkopf Microanalytical Laboratories (Woodside,N.Y.); samples for elemental analysis were Kogelruhr distilled. ¹ H and¹³ C NMR spectra were run on 270 MHz and 360 MHz instruments by SpectralData Services (Champaign, Ill.); proton spectrum lines are given invalues of δ. ESCA analyses were performed by Surface Science Corporation(Mountain View, Calif.).

A siloxane quaternary ammonium salt having general formula A is readilyprepared by a synthetic procedure which begins with aglycidyloxypropylheptamethyltrisiloxane and which is described in theexamples which follow. For convenience, each step of the reactionsequence comprises a separate example and is illustrated by a separatefigure.

EXAMPLE 1

Synthesis of 3-3-(2,3-Epoxypropoxy)propyl!-1,1,1,3,5,5,5-heptamethyltrisiloxane (I)(FIG. 1)

Although the starting material, 3-3-(2,3-epoxypropoxy)propyl!-1,1,1,3,5,5,5-heptamethyltrisiloxane(Compound I), can be obtained commercially, it was prepared by theprocedure which follows. A 500-ml, three-necked, round-bottomed flaskwas equipped with a stirrer, addition funnel, and condenser and wasflushed continuously with argon. The flask was charged with 22.5 g (0.22mole) of allyl glycidyl ether (Aldrich Chemical Company, Milwaukee,Wis.), and 50.0 g (0.22 mole) of3-hydro-1,1,1,3,5,5,5-heptamethyltrisiloxane (Huils Americas,Piscataway, N.J.) in 150 ml of xylene. The addition funnel was chargedwith a suspension of 2.8 g (0.03 mole) of hexachloroplatinic acid(Aldrich) in 140 ml of n-octyl alcohol. The hexachloroplatinic acidsuspension was added drop-wise to the flask, after which the resultingreaction mixture was heated at 100° C. overnight. The xylene then wasremoved by rotary evaporation at ambient temperature under reducedpressure. Selective extraction of the residue with hexane yielded theglycidyloxypropylheptamethyltrisiloxane or epoxy trisiloxane (CompoundI) after solvent removal. The yield was 68.4 g (94%). The elementalanalysis was as follows:

Theoretical: %C, 44.7; %H, 9.3; %Si, 26.8

Found: %C, 44.3; %H, 9.0; %Si, 26.5

The nuclear magnetic resonance data for the product were as follows:

¹ H NMR (CDCl₃):

0.01 (m, Si--H₃), 0.60 (m, Si--CH₂ --),

3.60 (m, ═CH--O)

EXAMPLE 2

Synthesis of Dimethyl Hexadecyl {2-Hydroxy-3-3-(1,3,3,3-tetramethyl-1-(trimethylsiloxy)disiloxanyl)-propoxy!propyl}Ammonium Chloride (II) (FIG. 2)

A 500-ml, three-necked, round-bottomed flask was equipped with astirrer, addition funnel, dry ice/acetone condenser, thermometer andelectric heating mantle. The flask was flushed continuously with argon.The flask was charged with 167.2 g (0.55 equivalent) of dimethylhexadecyl ammonium chloride (Sartomer Chemical Company, West Chester,Pa.), 0.028 g (0.27 milliequivalent) of triethylamine (Aldrich), and 250g of isopropanol. To the stirred flask contents 65.2 g of the epoxytrisiloxane of Example 1 was added over a ten-minute period. Thereaction mixture was stirred and heated at 80° C. for five hours to forma clear solution. The reaction mixture was cooled to ambient temperatureand flushed overnight with dry argon. The solvent and other low-boilingmaterials were removed by rotary evaporation at 45° C. The yield of thequaternary ammonium salt (Compound II), a light yellow oil, was 118 g(87%). The elemental analysis was as follows:

Theoretical: %C, 55.1; %H, 10.7; %Si, 12.6; %N, 2.1

Found: %C, 54.6; %H, 10.4; %Si, 12.1; %N, 1.8

The nuclear magnetic resonance data were as follows:

¹ H NMR (CDCl₃):

0.01 (m, Si--CH₃), 0.60 (m, Si--CH₂ --),

3.60 (m, ═CH--O), 2.86 (m, --N--CH₃)

EXAMPLE 3

Synthesis of Dimethyl Hexadecyl {3-3-(1,3,3,3-Tetramethyl-1-(trimethylsiloxy)disiloxanyl!-propoxylacetonyl}Ammonium Chloride (II) (FIG. 3)

A 250-ml, three-necked, round-bottomed flask was equipped with astirrer, addition funnel, and condenser. The flask was charged with 14.5g of chromium trioxide in 100 ml of water. To the flask was addeddrop-wise 50 g (0.07 mole) of Compound II in 50 ml of tetrahydrofuran.The reaction mixture was stirred overnight and then poured into 200 mlof ice water. The resulting mixture was extracted with diethyl ether.The ether extract was dried and the solvent removed on a rotaryevaporator under vacuum to yield 47 g (94%) of Compound III, a lightyellow oil. The following elemental analysis was obtained:

Theoretical: %C, 55.3; %H, 10.4; %Si, 12.7; %N, 2.1

Found: %C, 54.7; %H, 10.0; %Si, 12.0; %N, 1.7

An infrared spectrum of the material (neat) showed maxima at 1740 cm⁻¹(C═O) and 1063 cm⁻¹ (N--C). The nuclear magnetic resonance data were asfollows:

¹ H NMR (CDCl₃):

0.01 (m, Si--CH₃), 0.60 (m, Si--CH₂ --),

3.6 (m, ═CH₂ --O--)

EXAMPLE 4

Synthesis of Dimethyl Hexadecyl {3-3-(1,3,3,3-Tetramethyl-1-(trimethylsiloxy)disiloxanyl)-propoxy!acetonyl}Ammonium p-Toluenesulfonate (IV) (FIG. 4)

A 250-ml, three-necked, round-bottomed flask equipped with a stirrer,addition funnel, and condenser was charged with 50.0 g (74 mmole) ofCompound III dissolved in 150 ml of isopropanol. To the solution atambient temperature was added 57.5 g (0.30 mole) of p-toluenesulfonicacid, sodium salt (Aldrich). The reaction mixture was stirred at ambienttemperature for eight hours, after which 50 ml of water was added andthe reaction mixture extracted with diethyl ether. Removal of the driedether extract by rotary evaporation gave 53.4 g (94%) of Compound IV.The following elemental analysis was obtained:

Theoretical: %C, 57.9; %H, 10.3; %Si, 11.2; %S, 4.1; %N, 1.8

Found: %C, 57.6; %H, 10.6; %Si, 11.6; %S, 3.9; %N, 2.1

An infrared spectrum of the material (neat) showed maxima at 1740 cm⁻¹(C═O) and 1063 cm⁻¹ (N--C). The nuclear magnetic resonance data for theproduct were as follows:

¹ H NMR (CDCl₃):

0.01 (m, Si_(--CH) ₃), 0.60 (m, Si--CH₂ --),

3.6 (═CH₂ --O--)

EXAMPLE 5

Synthesis of Benzyl-{2-hydroxy-3-3-(1,3,3,3-tetramethyl-1-(trimethylsiloxy)-disiloxanyl)propoxy!propyl}amine(V) (FIG. 5)

A 500-ml, three-necked, round-bottomed flask equipped with a stirrer,addition funnel, and condenser was charged with 100 g (0.30 mole) of theepoxy trisiloxane (Compound I) of Example 1 dissolved in 200 ml ofisopropanol. The addition funnel was charged with a solution of 42.8 g(0.4 mole) of benzylamine (Aldrich) in 100 ml of isopropanol; thesolution was added drop-wise to the flask contents at room temperature.The resulting reaction solution was heated at 80° C. for eight hours,after which time the solvent was removed under reduced pressure using arotary evaporator. The residue, an oil, was passed through a shortsilica column using 10% ethyl acetate in hexane as eluent. The yield ofCompound V, a colorless oil, was 127.8 g (97%). The following elementalanalysis was obtained:

Theoretical: %C, 48.7; %H, 9.2; %Si, 18.9; %N, 3.1

Found: %C, 48.4; %H, 9.5; %Si, 18.4; %N, 3.0

An infrared spectrum of the material (neat) showed maxima at 3300 cm⁻¹(OH) and 1063 cm⁻¹ (C--N). The nuclear magnetic resonance data were asfollows:

¹ H NMR (CDCl₃):

0.01 (m, Si--CH₃), 0.60 (m, Si--CH₂ --),

3.6 (m, ═CH₂ --O--), 3.56 (m, Ar--CH₂ --N)

EXAMPLE 6

Synthesis of Dimethyl Benzyl {3-3-(1,3,3,3-Tetramethyl-1-(trimethylsiloxy)disiloxanyl)-propoxy!acetonyl}Ammonium Sulfate (VI) 5 (FIG. 6)

The hydroxy group in Compound V from Example 5 was oxidized to theketone essentially as described in Example 3. An 80.0-g portion of theresulting ketone was charged to a 500-ml, three-necked, round-bottomedflask 10 fitted with a stirrer, addition funnel, and condenser was added80.0 g (0.18 mole) of the above ketone product dissolved in 200 ml ofdimethyl sulfate (Aldrich). The solution was heated at reflux for eighthours after which the solvent and other volatiles were removed underreduced pressure in a rotary evaporator. The residual oil was passedthrough a short silica gel column 1 5 using 30% ethyl acetate in hexaneas eluent. Compound VI was obtained as a colorless oil. The yield was78.4 g (92%). An infrared spectrum of the material (neat) showed amaximum at 1730 cm⁻¹ (C═O). The nuclear magnetic resonance data for theproduct were as follows:

¹ H NMR (CDCl₃):

0.01 (m, Si--CH₃), 0.60 (m, Si--CH₂ --),

2.85 (m, ═N--CH₃), 3.56 (m, Ar--CH₂ --N)

EXAMPLE 7

Synthesis of Dimethyl Benzyl {2,2-Dimethyl-3-3-(1,3,3,3-Tetramethyl-1-(trimethylsiloxy)disiloxanyl!-25propoxylpropyl} Ammonium Chloride (VII) (FIG. 7)

In a thick walled glass tube having a sealed bottom were placed 20.0 g(0.04 mole) of Compound VI from Example 6 in 40 ml of benzene (Aldrich),0.4 ml of water, and 8.6 g (0.12 mole) trimethyl aluminum (Aldrich). Thetop of the glass tube was sealed and the tube was placed in a stainlesssteel bomb which was then heated at 140° C. for eight hours. Aftercooling to ambient temperature, the glass tube was carefully opened andthe contents were poured drop-wise into a mixture of 200 ml diethylether and 50 ml of 0.5N hydrochloric acid chilled in an ice bath. Theorganic layer was separated and dried. Solvents were removed underreduced pressure using a rotary evaporator. Compound VII was obtained;the yield was 9.5 g (46%). The nuclear magnetic resonance data for theproduct were as follows:

¹ NMR (CDCl₃):

0.01 (m, Si--H₃), 0.60 (m, Si--CH₂ --),

0.81 (m, ≡C--CH₃), 2.85 (m, ═N--CH₃),

3.56 (m, Ar--CH₂ --N)

EXAMPLE 8

Synthesis of Dimethyl 4Hexadecylphenylmethyl {2,2-Dimethyl-3-3-(1,3,3,3-Tetramethyl-1-(trimethylsiloxy)disiloxanyl)-propoxy!propyl}Ammonium Chloride (VI) (FIG. 8)

To a 500-ml, three-necked, round-bottomed flask fitted with a stirrer,addition funnel, and condenser being continuously flushed with argon wascharged 20.0 g (0.04 mole) of Compound VII from Example 7, 15.6 g (0.06mole) 1-chlorohexadecane (Aldrich), and 200 ml hexane. The resultingreaction mixture was cooled to 0° C. using a crushed ice/salt bath and2.0 g of anhydrous aluminum chloride was added to the stirred mixture.After 30 minutes an additional 6.0 g of aluminum chloride (0.06 moletotal) was added and the reaction mixture slowly heated to 60° C. over afour-hour period. The reaction mixture then was allowed to cool. Aftercooling, 100 g of crushed ice and 100 ml of water were slowly added. Theorganic layer was separated and washed with dilute hydrochloride acid,dried and the solvent removed under vacuum on a rotary evaporator. Theoil was run through a short silica gel column using 30% ethyl acetate inhexane as eluent. Removal of the solvent gave 23.9 g (82%) of acolorless oil, Compound VIII. The following elemental analysis wasobtained:

Theoretical: %C, 62.7; %H, 11.6; %Si, 12.1; %N, 2.0

Found: %C, 62.1; %H, 11.2; %SI, 12.4; %N, 2.4

The nuclear magnetic resonance data were as follows:

¹ H NMR (CDCl₃):

0.01 (m, Si--CH₃), 0.60 (m, Si--CH₂ --),

0.81 (m, ≡C--CH₃), 2.85 (m, ═N--CH₃),

3.56 (m, Ar--CH₂ --N),

6.94 (m, p-substituted benzene)

EXAMPLE 9

Synthesis of Dimethyl 4-Hexadecylphenylmethyl {2,2-Dimethyl-3-3-(1,3,3,3-Tetramethyl-1-(trimethylsiloxy)disiloxanyl)-propoxy!propyl}Ammonium p7Toluenesulfonate (IX) (FIG. 9)

The procedure of Example 4 was repeated with Compound VIII. A colorlessoil was obtained in 94% yield. The following elemental analysis wasobtained:

Theoretical: %C, 59.8; %H, 10.5; %Si, 10.2; %N, 1.7

Found: %C, 59.5; %H, 10.7; %Si, 10.6; %N, 1.4

The nuclear magnetic resonance data were as follows:

¹ H NMR (CDCl₃):

0.01 (m, Si--CH₃), 0.60 (m, Si--CH₂ --),

0.81 (m, ≡C--CH₃), 2.85 (m, ═N--CH₃),

3.56 (m, Ar--CH₂ --N),

6.94 (m, p-substituted benzene)

EXAMPLE 10

Synthesis of Dimethyl 4-Hexadecylphenylmethyl{3-3-(1,3,3,3-Tetramethyl-1-(trimethylsiloxy)-disiloxanyl)-propoxy!acetonyl}Ammonium Chloride (X) (FIG. 10)

The procedure of Example 8 was repeated with 20.0 g (0.03 mole) ofCompound VI from Example 6 as starting material. The yield of CompoundX, a colorless oil, was 21.4 g (81%). The following elemental analysiswas obtained:

Theoretical: %C, 62.5; %H, 10.4; %Si, 11.5; %N, 1.9

Found: %C, 62.3; %H, 10.6; %Si, 11.2; %N, 1.7

The nuclear magnetic resonance data were as follows:

¹ H NMR (CDCl₃):

0.01 (m, Si--CH₃), 0.60 (m, Si--CH₂ --),

2.85 (m, ═N--CH₃), 3.56 (m, Ar--CH₂ --N),

6.94 (m, p-substituted benzene)

The antimicrobial activity of five of the compounds of the presentinvention described in the preceding examples, the thermal stability ofsuch compounds, the preparation of nonwoven webs from thermoplasticcompositions which include such antimicrobial compounds, and thebiological evaluation of such nonwoven webs are described in theexamples which follow.

EXAMPLE 11

Antimicrobial Activities of Various Compounds of the Present Invention

The antimicrobial activities of Compounds II, III, IV, IX, and X weretested at a concentration of 10⁻² g/l. The compound to be tested wasadded to a 50-ml centrifuge tube containing 100 μl of a bacterial stocksuspension in which the microorganism concentration was 2.8×10⁸CFU's/ml. Each tube was maintained at ambient temperature for fourhours. At the end of the four-hour period, 30 ml of Letheen broth(Difco, USA) was added to each centrifuge tube. The tubes were vortexedat a setting of 4 G for one minute. The survival of bacteria in thesuspension was determined by plating suitable dilutions of sedimentedmaterial on Letheen agar (Difco, USA) and counting the number of CFU'safter 18 hours of incubation at 37° C. The survival of bacteria wasdetermined by comparing the number of CFU's per ml observed in bacterialsuspensions after four hours of incubation in the presence of the testcompound and the number of CFU's per ml of the same bacterialsuspensions in the control tubes. Such comparisons were done bycalculating the log drop for each compound as follows:

Log drop=Log 100-(surviving CFU's/initial CFU's)×100!

See, e.g., R. A. Robison et al., Appl. Environ. Microbiol., 54, 158(1988). The antibacterial activities of the five compounds aresummarized in Table 1.

                  TABLE 1                                                         ______________________________________                                        Antimicrobial Activity of Five Compounds                                      Reported as Log Drop Values                                                           Log Drop of Bacterial Strain                                          Compound  Escherichia Coli                                                                          Staphylococcus Epidermidis                              ______________________________________                                        II        3.5         4.0                                                     III       3.5         4.1                                                     IV        3.7         4.2                                                     IX        3.8         4.4                                                     X         3.8         4.4                                                     ______________________________________                                    

As the data in Table 1 show, all five of the compounds possess excellentantibacterial activity.

EXAMPLE 12 Thermal Stability of Five Compounds of the Present Invention

Because the compounds of the present invention are intended to be usedin melt-extrusion processes, thermal stability is of interest.Accordingly, the thermal stability of each of Compounds II, III, IV, IX,and X was studied. Each compound was placed in a glass tube under anitrogen atmosphere. The tube was sealed and heated at 232° C. for 30minutes. The contents of each tube then were analyzed by means of a highpressure liquid chromatography system comprising an ISCO Model 2350pump, A Waters RCM pack unit containing a Waters C18 5-μ column, aWaters Model 410 differential refractometer, and a Waters Model 745 datamodule integrator. The solvent employed was deaerated 10 percent waterin methanol. The results are summarized in Table 2 which gives thepercent decomposition by weight.

                  TABLE 2                                                         ______________________________________                                        Thermal Stability of Five Compounds                                           Reported as Percent Decomposition by Weight                                   Compound      % Decomposition                                                 ______________________________________                                        II            36                                                              III           32                                                              IV            8                                                               IX            1                                                               X             3                                                               ______________________________________                                    

The thermal stability of Compounds II and III, while not exceptional, issufficient to permit the use of the compounds in melt-extrusionprocesses. This will be especially true in cases where residence timesare shorter than 15 minutes and/or extrusion temperatures are lower than232° C. Because the data in Table 2 resulted from a 30-minute heatingperiod, compound decomposition during melt processing to form nonwovenwebs should be less.

Compounds IV, IX, and X, on the other hand, have good to excellentthermal stability. From FIGS. 2, 3, 4, 9, and 10, it is seen that thesecompounds have fewer β-hydrogen atoms than Compounds II and m and/or theanion is a weak base. These relationships perhaps are best understood byreference to Table 3. Table 3 lists for each of the five compounds thestructures associated with the β-carbon atoms, the total number ofβ-hydrogen atoms, and the anion. Because there are two β-carbon atoms ineach compound, they have been distinguished as follows: the β-carbonatom on the silicon atom side of the nitrogen atom is referred to asbeing in the "ether moiety," whereas the β-carbon atom on the side"opposite" that of the ether moiety is referred to as being in the"terminal moiety."

                  TABLE 3                                                         ______________________________________                                        β-Carbon Structures and Anions                                           for Five Compounds of the Present Invention                                           β-Carbon Structure                                                                     Terminal  Total                                         Compound  Ether Moiety                                                                              Moiety    β-H's                                                                          Anion                                   ______________________________________                                        II                                                                                       ##STR12##  CH.sub.2  3     Cl.sup.⊖                        III                                                                                      ##STR13##  CH.sub.2  2     Cl.sup.⊖                        IV                                                                                       ##STR14##  CH.sub.2  2     Ts.sup.⊖                        IX                                                                                       ##STR15##  C         0     Ts.sup.⊖                                   ##STR16##  C         0     Cl.sup.⊖                        ______________________________________                                    

Thus, compounds having no β-hydrogen atoms and/or a weak base anionrepresent more thermally stable embodiments.

EXAMPLE 13 Preparation of Polypropylene Spunbonded Webs

Polypropylene nonwoven spunbonded webs were prepared on pilot scaleequipment essentially as described in U.S. Pat. No. 4,360,563. Theextrusion temperature was approximately 232° C. The process wassubstantially anaerobic, even though special efforts to exclude oxygenwere not taken, and process times typically did not exceed 15 minutes.The webs were thermally point-bonded. The basis weight of each web was27 g/m².

A first, negative control web was prepared from polypropylene alone (WebA).

Seventeen webs then were prepared from a mixture of polypropylene and acompound of the present invention (Webs B-R, inclusive). Polypropylenepellets were simply surface-coated with the siloxane quaternary ammoniumsalt prior to extrusion. After formation and thermal point-bonding, thewebs received no further treatment or processing. Five differentcompounds were evaluated. Each compound was incorporated at threedifferent levels, with two of the compounds being incorporated at afourth level.

As a second, positive control, a portion of the control web was treatedtopically with a commercially available siloxane quaternary ammoniumsalt having the following formula: ##STR17## in which Q₃.sup.⊕ has theformula, ##STR18## and .sup.⊖ Y₃ is chloride. The add-on level was 0.9percent by weight, based on the dry weight of the web (Web S).

The compounds and compound levels employed in the thermoplasticcompositions from which nonwoven webs B-R, inclusive, were prepared aresummarized in Table 4.

                  TABLE 4                                                         ______________________________________                                        Compounds and Compound Levels Employed                                        in the Preparation of Webs B-R                                                                      Compound Level                                          Web         Compound  (Weight-Percent)                                        ______________________________________                                        B           II        0.5                                                     C           II        0.7                                                     D           II        1.0                                                     E           III       0.5                                                     F           III       0.7                                                     G           III       1.0                                                     H           IV        0.5                                                     I           IV        0.7                                                     J           IV        1.0                                                     K           IX        0.5                                                     L           IX        0.7                                                     M           IX        1.0                                                     N           IX        1.5                                                     O           X         0.5                                                     P           X         0.7                                                     Q           X         1.0                                                     R           X         1.5                                                     ______________________________________                                    

Many of the webs listed in Table 4 were subjected to electronspectroscopy for chemical analysis (ESCA). The ESCA data were collectedby Surface Science Laboratories, Inc., Mountain View, Calif., using aHewlett-Packard 5950 B spectrometer with a monochromatic aluminumK-alpha x-ray source. The scans were done with the open aperture settingfor high sensitivity (low resolution). The x-ray power setting was600-800 watts and charge neutralization was accomplished with a floodgun setting of 13 electron volts. The vacuum utilized was 10⁻⁸ Torr. Thearea analyzed was about 1×4 mm and the sampling depth was about 100 Å.The results are summarized in Table 5; in the table, atom-%concentration is to a depth of approximately 100 Å.

                  TABLE 5                                                         ______________________________________                                        ESCA Analysis of Nonwoven Webs                                                Concentration in Atom-%                                                       Found              Calculated                                                 Web     Si     C         N   Si      C    N                                   ______________________________________                                        B       10.0   68.2      1.8 12.6    55.1 2.1                                 D       10.4   67.8      1.9 12.6    55.1 2.1                                 E       11.0   68.0      1.9 12.7    55.3 2.1                                 F       12.0   67.0      2.2 12.7    55.3 2.1                                 G       12.0   66.8      1.9 12.7    55.3 2.1                                 H       10.0   68.0      1.5 11.2    57.9 1.8                                 J       10.5   67.8      1.6 11.2    57.9 1.8                                 K       10.0   62.4      1.5 10.2    59.8 1.7                                 M       10.0   62.6      1.6 10.2    59.8 1.7                                 N       10.0   62.4      1.6 10.2    59.8 1.7                                 O       11.5   64.4      1.8 12.1    61.2 2.0                                 Q       11.8   65.2      1.9 12.1    61.2 2.0                                 R       12.0   64.6      1.9 12.1    61.2 2.0                                 S       14.0   65.0      2.3 --      --   --                                  ______________________________________                                    

It is evident from Table 5 that a substantial portion of the surfaces ofthe fibers of the nonwoven webs studied consists of the antimicrobialcompound present in the thermoplastic composition from which the webswere prepared. That is, the compounds of the present invention appear tohave surface segregated to a remarkable and unexpected degree.

In an effort to aid in the visualization of the effectiveness orcompleteness of such surface segregation, the ratios of silicon found totheoretical silicon and nitrogen found to theoretical nitrogen werecalculated from the data in Table 5 as follows:

Si=100×(silicon conc'n. found/theoretical silicon conc'n.)

N=100×(nitrogen conc'n. found/theoretical nitrogen conc'n.)

Thus, the calculations give the ESCA value of either silicon or nitrogenas a percentage of the theoretical value for that element. Thesecalculations are summarized in Table 6, which also includes the datafrom Table 4 for convenience.

                  TABLE 6                                                         ______________________________________                                        Silicon and Nitrogen Ratios from ESCA Data                                    Compound and Level   Found: Calc'd. Ratios                                    Web     Compound  Weight-%   Silicon                                                                             Nitrogen                                   ______________________________________                                        B       II        0.5        79    86                                         D       II        1.0        83    90                                         E       III       0.5        87    90                                         F       III       0.7        94    100                                        G       III       1.0        94    90                                         H       IV        0.5        89    83                                         J       IV        1.0        94    89                                         K       IX        0.5        98    88                                         M       IX        1.0        98    94                                         N       IX        1.5        98    94                                         O       X         0.5        95    90                                         Q       X         1.0        98    95                                         R       X         1.5        99    95                                         ______________________________________                                    

The data in Table 6 were plotted as bar graphs, grouped by compoundnumber, and are presented as FIGS. 11-15, inclusive. Thus, FIG. 11 is abar graph of the silicon and nitrogen ESCA values for Compound II atlevels of 0.5% and 1.0% by weight, expressed as a percentage of thetheoretical values, i.e., the data for webs B and D. FIG. 12 is a bargraph of the data for webs E, F, and G; FIG. 13 is a bar graph of thedata for webs H and J; FIG. 14 is a bar graph of the data for webs K, M,and N; and FIG. 15 is a bar graph of the data for webs O, Q, and R.

The basis for the statement above that the compounds of the presentinvention surface segregate to a remarkable and unexpected degree isclear from Table 6 and FIGS. 11-15. If the surfaces of the fibers of thenonwoven webs were completely covered by or with an antimicrobialcompound of the present invention, the ESCA values for silicon andnitrogen would be equal to the theoretical values. Stated differently,the ESCA values would be equal to the theoretical values if theantimicrobial compound were present on the surfaces of the fibers to anapproximate depth of 100 Å. Even with the experimental error inherent inESCA analyses, the 100 Å portion of the fiber surfaces measured by ESCAconsist essentially of antimicrobial compound. Equally significant isthe fact that essentially complete coverage of the fiber surfaces wasobtained with several compounds even at levels of 0.5 percent by weight.For those compounds, it is evident that lower levels can be used withoutsacrificing the antimicrobial activity of the nonwoven webs.

The fact that the antimicrobial compounds are found in such highconcentrations to a depth of 100 Å (and possibly deeper) stronglysuggests that the antimicrobial properties demonstrated to be present atthe surfaces of the fibers are likely to be durable. That is, suchcompounds form an extended antimicrobial surface, i.e., an antimicrobialsurface which extends below the air/fiber interfacial surface. Becauseof the high concentrations of antimicrobial compounds near (i.e., within100Å of) the fiber interfacial surfaces, compound which may be removedfrom the interfacial surface by dissolution in a solvent or otherprocess can be replenished from the extended surface reservoir ofantimicrobial compound.

EXAMPLE 14

Antimicrobial Activities of the Nonwoven Webs of Example 13

The bacterial strains Escherichia coli (ATCC No. 13706) andStaphylococcus epidennidis (ATCC No. 1859) were used to evaluate theantibacterial activity of the nonwoven webs prepared in Example 13.Bacterial suspensions containing about 10⁸ colony forming units (CFU's)per ml were obtained by collecting overnight growth from tryptic soyagar (Difco, USA) in saline.

Each web was cut into 1"×1" (about 2.5 cm×2.5 cm) samples. Each samplewas placed in a 50-ml centrifuge tube, to which was added 100 μl of abacterial stock suspension containing 2.8×10⁸ CFU's/ml. Samples wereleft at ambient temperature for four hours. At the end of the four-hourperiod, 30 ml of Letheen broth (Difco, USA) was added to each centrifugetube. The tubes were vortexed at a setting of 4G for one minute. Thesurvival of bacteria in the presence of the nonwoven web was determinedas described in Example 11. The antibacterial activities of the webs ofExample 13 are summarized in Table 7.

                  TABLE 7                                                         ______________________________________                                        Antibacterial Activities of the Nonwoven Webs of Example 13                   Reported as Log Drop Values                                                          Log Drop Values for Bacterial Strain                                   Web      Escherichia Coli                                                                          Staphylococcus Epidermidis                               ______________________________________                                        A        No Change   No Change                                                B        1.2         1.9                                                      C        1.2         1.9                                                      D        1.8         2.2                                                      E        1.6         2.2                                                      F        1.6         2.2                                                      G        1.8         2.3                                                      H        3.1         3.8                                                      I        3.1         3.8                                                      J        3.5         4.0                                                      K        3.8         4.4                                                      L        3.8         4.4                                                      M        4.0         4.5                                                      N        4.1         4.5                                                      O        3.8         4.4                                                      P        3.8         4.4                                                      Q        4.1         4.5                                                      R        4.1         4.5                                                      S        0.9         1.6                                                      ______________________________________                                    

A careful study of the data in Table 7 makes it clear that the compoundspreviously demonstrated to be at the surfaces of the fibers making upthe nonwoven webs are effective as antimicrobial agents. In order toassist in the visualization and appreciation of the data, however, twobar graphs were prepared and are included as FIGS. 16 and 17. FIG. 16 isa three-dimensional bar graph of the log drop data for Eschenchia coli,with the data being grouped by compound level; the figure also includesthe log drop data for the compounds in solution and the topicallyapplied compound. FIG. 17 is similar to FIG. 16, except that the logdrop data are for Staphylococcus epidernidis.

FIGS. 16 and 17, in conjunction with Table 7, clearly support at leastthe following conclusions:

(1) all of the internally incorporated compounds resulted in fibershaving antimicrobial activity as good as or better than the topicallyapplied compound;

(2) of the five compounds investigated as internal additives, CompoundsIV, IX, and X were more effective in imparting antimicrobial propertiesto the surfaces of the fibers;

(3) Compound IV was almost as effective as an internal additive as whenused in solution;

(4) Compounds IX and X were as effective or more effective as internaladditives as when used in solution; and

(5) the effectiveness of Compounds IX and X as internal additives doesnot appear to be concentration dependent at the levels studied.

Two particularly interesting aspects of FIGS. 16 and 17 are worthy offurther comment. First, FIGS. 16 and 17 dramatically illustrate therelatively constant high effectiveness of Compounds IX and X.Consequently, levels of these compounds below 0.5 percent by weightclearly can be used. Based on the increases in effectiveness withincreasing concentration of all five compounds, levels as low as 0.1percent by weight should be feasible. Depending on the level ofantimicrobial activity desired, even lower levels probably can be used.Although levels above 1.5 percent by weight also can be used,significant increases in antimicrobial activity would not be expected.However, such higher levels may be useful in instances where it isdesired to provide a reservoir of antimicrobial compound at the surfacesof the fibers of the nonwoven webs. Thus, levels of from about 0.1 toabout 3 percent by weight represent a practical range.

Second, the increases in log drop for Compounds II, III, and IV aregenerally similar. Moreover, the antimicrobial effectiveness of each ofthese compounds when incorporated into a nonwoven web appears to bedirectly proportional to the thermal stability of the compound. That is,the compounds having higher thermal decomposition also resulted in lowerantimicrobial activity, even though such activity still is equal to orgreater than the activity of the topically applied compound.

The antimicrobial activity of the compounds, when incorporated intononwoven webs, is less than what have been expected, based only on theESCA analyses; compare FIGS. 11-13 with FIGS. 16 and 17 (or compareTables 5 and 6 with Table 7). This is particularly true for compounds IIand III. While the ESCA analyses gave values for silicon and nitrogenwhich were at least 80 percent of the theoretical values, thedifferences in log drop values were much greater. For example, the logdrop values for Compound II with E. coli and S. epidermidis were 3.5 and4.0 respectively (see Table 1). The corresponding log drop valuesobtained upon incorporating Compound II into the fibers of a nonwovenweb, however, were lower by approximately 2 (1.7-2.3 and 1.8-2.1,respectively). The log drop values for Compound III with E. coli and S.epidermidis were 3.5 and 4.1 respectively (see Table 1). Thecorresponding log drop values obtained upon incorporating Compound IIIinto the fibers of a nonwoven web also were lower by approximately 2(1.7-1.9 and 1.8-1.9, respectively). Since each log drop unit representsa ten-fold difference, the lower log drop values just describedrepresent an approximately 100-fold difference.

The explanation for the apparent anomaly between the antimicrobialeffectiveness observed upon incorporating Compounds II and III intononwoven webs and the ESCA data is believed to be based on the nature ofthe products which result upon the thermal degradation of thesecompounds. Based on thermogravimetric analyses or TGA (not reported), itwas determined that the compounds of the present invention in generaldid not undergo significant weight loss upon being heated toapproximately 230° C. From the results described in Example 12, it isclear that Compounds II and III do, in fact, experience some thermaldegradation. Because of the TGA results, however, it appears that thethermal degradation products are not significantly volatile under theconditions encountered in the melt-extrusion process, even though noattempt was made to characterize or identify such products. It isassumed, therefore, that such products are at least in part carried tothe surfaces of the fibers, or that degradation occurs at the surfacesof the fibers, and such products lack antimicrobial propertiessufficient to have an effect upon the antimicrobial effectiveness of thenonwoven webs. However, the presence of degradation products at thesurfaces of the fibers still would contribute to the silicon andnitrogen values observed by ESCA analyses. FIGS. 16 and 17 make it clearthat the effect of thermal degradation, whenever it occurs, can bepartially offset by increasing the level of the compound in thethermoplastic composition from which the nonwoven web is prepared.Whenever permitted by process requirements, reducing melt extrusiontemperatures and/or residence times in the melt will contribute toreducing the extent of thermal degradation.

While the specification has been described in detail with respect tospecific embodiments thereof, it will be appreciated that those skilledin the art, upon attaining an understanding of the foregoing, mayreadily conceive of alterations to, variations of, and equivalents tothese embodiments. Accordingly, the scope of the present inventionshould be assessed as that of the appended claims and any equivalentsthereto.

What is claimed is:
 1. A fiber having antimicrobial properties made froma melt-extrudable composition of which comprises:at least onethermoplastic polyolefin adapted to be shaped into a product by meltextrusion; and at least one additive which is adapted to surfacesegregate upon extrusion of said composition to impart antimicrobialproperties to a surface of said product, wherein said additive haseither the general formula A, ##STR19## wherein: (1) each of R₁ -R₇ isindependently selected from the group consisting of monovalent C₁ -C₂₀alkyl, phenyl, and phenyl-substituted C₁ -C₂₀ alkyl groups, in whicheach phenyl can be substituted or unsubstituted; (2) each of R₈ and R₉is a monovalent group independently selected from the group consistingof (a) hydrogen and (b) monovalent alkyl, cycloalkyl, aryl, andheterocyclic groups and combinations thereof having up to about 30carbon atoms, except that both R₈ and R₉ cannot be hydrogen; or, whentaken together in combination with the carbon atom to which they areattached, R₈ and R₉ represent a carbonyl group; (3) each of R₁₀ and R₁₁is a methyl group; (4) a represents an integer from 1 to about 20; (5) brepresents an integer from 1 to about 20; (6) Z is a monovalent grouphaving from about 8 to about 30 carbon atoms and selected from the groupconsisting of alkyl, cycloalkyl, aryl, and heterocyclic groups, andcombinations thereof, wherein Z is terminated by an alkyl moiety whichincludes at least about 8 carbon atoms in a single continuous chain; (7)Y₁ is an anion which does not cause the thermal instability of theadditive to be more than about 35 weight percent decomposition duringmelt extrusion; and (8) said additive has a molecular weight of fromabout 600 to about 1,700; or the general formula B, ##STR20## wherein:(1) each of R₂₀ -R₂₃ is independently selected from the group consistingof monovalent C₁ -C₂₀ alkyl, phenyl, and phenyl-substituted C₁ -C₂₀alkyl groups, in which each phenyl can be substituted or unsubstituted;(2) n represents an integer of from 1 to about 19; (3) each of Q₁ and Q₂represents an independently selected quaternary ammonium group havingthe general formula, ##STR21## in which: (a) R₂₄ is a monovalent alkylgroup having from about 8 to about 30 carbon atoms, at least about 8carbon atoms of which make up a single continuous chain:(b) R₂₅ and R₂₆are methyl groups; (c) each of R₂₇ and R₂₈ is a monovalent groupindependently selected from the group consisting of (i) hydrogen and(ii) monovalent alkyl, cycloalkyl, aryl, and heterocyclic groups andcombinations thereof having up to about 30 carbon atoms, except thatboth R₂₇ and R₂₈ cannot be hydrogen; or, when taken together incombination with the carbon atom to which they are attached, R₂₇ and R₂₈represent a carbonyl group, (d) c represents an integer of from 2 toabout 20; and (e) d represents an integer of from 2 to about 20; (4) Y₂represents an anion which does not cause the thermal instability of theadditive to be more than about 35 weight percent decomposition duringmelt extrusion; and (5) said additive has a polydispersity of up toabout 3.0 and a weight-average molecular weight of from about 800 toabout 2,000;wherein said additive is present in said melt-extrudablecomposition in an amount sufficient to impart antimicrobial activity tothe surfaces of a shaped article prepared therefrom by a melt-extrusionprocess.
 2. The fiber of claim 1, in which Z is a monovalent grouphaving the general formula, ##STR22## in which each of R₁₂ -R₁₄ is anindependently selected monovalent alkyl group wherein the total numberof carbon atoms in all of R₁₂ -R₁₄ is from about 6 to about 28 and atleast one of R₁₂ -R₁₄ contains at least about 6 carbon atoms in a singlecontinuous chain.
 3. The fiber of claim 1, in which Z is a monovalentgroup having the general formula, ##STR23## in which each of R₁₅ -R₁₉ isa monovalent group independently selected from the group consisting ofhydrogen and alkyl, and wherein the total number of carbon atoms in allof R₁₅ -R₁₉ is from about 8 to about 23, with at least one of R₁₅ -R₁₉having at least about 6 carbon atoms in a single continuous chain. 4.The fiber of claim 3, in which each of R₁₅, R₁₆, R₁₈, and R₁₉ ishydrogen and R₁₇ is hexadecyl.
 5. The fiber of claim 1, in which each ofY₁ and Y₂ independently is selected from the group consisting of a weakbase.
 6. The fiber of claim 1, in which said additive has the formula,##STR24##
 7. The fiber of claim 1, in which said additive has theformula, ##STR25##
 8. The fiber of claim 1, in which said additive hasthe formula, ##STR26##
 9. The fiber of claim 1, in which said additiveis present in said melt-extrudable composition at a level of from about0.1 to about 3 percent by weight, based on the weight of thethermoplastic polyolefin.
 10. The fiber of claim 1, in which saidthermoplastic polyolefin is polyethylene or polypropylene.